# PROBLEM 1: If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. 
# The sum of these multiples is 23. Find the sum of all the multiples of 3 or 5 below 1000.

def sum_multiple(n,limit)
  sum = 0;
  i = 0;
  while (i < limit)
    if (i % n == 0)
      sum += i
    end
    i += 1
  end
  sum
end

limit = 1000
puts sum_multiple(3,limit) + sum_multiple(5,limit) - sum_multiple(15,limit)